1. Field of the Invention
This invention relates to a process for separating a slurry comprising fine solids, polar liquids and premium oil, the slurry produced by high temperature hydrogenation of a solid, hydrocarbonaceous fuel, into a first fraction comprising the premium oil and a second fraction comprising the fine solids and polar liquids.
2. Description of the Prior Art
The high temperature hydrogenation of solid, hydrocarbonaceous fuels, such as the liquefaction of coal, produces a feed slurry, comprising not only premium liquid oil but also various solids, e.g., ash, inorganic sulfur, etc. and other liquids, e.g., polar liquids, etc. Removal or separation of these materials, especially the fine solids from the premium oil, is a major problem and has been the subject of much research.
British Pat. No. 312,657 discloses an apparatus and process for the separation from solid residues of oils obtained in the destructive hydrogenation varieties of coal, tars, mineral oils and the like. The apparatus comprises a vertical column with a settling vessel attached to its top and a worm gear attached to its bottom. The process comprises introducing a slurry of solid residues and oils into the column at or near the column top and a solvent, typically benzene, into the column at or near the column bottom such that the solvent, as it passes up the column, extracts from the slurry, as it passes down the column the oils. The solid residues are removed as a powder from the bottom of the column by the worm gear while the oils are removed from the top of the column as an overflow from the settling vessel.
Demex is a process for the removal of metals (generally chelated by a ligand such as porphyrin) and petroleum asphaltene from heavy residua of certain asphaltic base crudes. Rev. Inst. Mex. Petrol., 6(1), 36-46 (1974). Although Demex involves countercurrent extraction within a vertical column, it is not designed for use with solid, hydrocarbonaceous fuel-derived oil (feed slurry), especially oil containing large amounts of fine solids.
Sze and Snell, U.S. Pat. Nos. 3,852,182 and 3,856,675, teach a fine solids removal process comprising contacting coal-derived oil with a promoter liquid in a mixing zone and then transferring the resulting liquid mixture to a gravity settling zone. The promoter liquid has a characterization factor of at least 9.75 and a preferred 5 volume percent distillation temperature of at least 400.degree. F.
Two papers delivered by Gorin et al. at the Spring Meeting Division of Fuel Chemistry, ACS, Philadelphia, PA, Apr. 6-11, 1975, teach a fine solids removal process comprising adding a solvent to a stirred mix tank of coal liquefaction product. The resulting liquid mixture is then transferred to a gravity settling vessel wherein impurities are removed. This process is similar to that taught by Sze and Snell but differs in the operating pressure, the latter requiring greater pressures.
Kerr-McGee (U.S. Pat. Nos. 3,607,716 and 3,607,717) teaches a variation on the gravity settling process described by both Gorin et al. and Sze and Snell comprising removal from a coal liquefaction product fine solids using a solvent heated to a super-critical temperature. This process differs from others in that the solids settle in a dense phase gas (the solvent under super-critical conditions). The fine solids are contained in the extraction residue.